installing buddypress 1.2.3 on wordpress mu 2.9.2 = blank page

On a fresh install of wordpress mu 2.9.2, I can’t seem to get buddypress 1.2.3 to activate properly.

I get a blank page when after I activate the plugin. I’ve done it through the “Add New” option in the WP MU back-end. I’ve also uploaded the contents of the zip file via FTP. Same result. No other plugins are active — s2member and formidable are there though inactive.

When I try to go to the WordPress admin screen, I get a 500 Internal Server Error:

Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator, support@apollohosting-inc.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.

More information about this error may be available in the server error log.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.